Can't reuse maps. Error: "This map is corrupted."

They are named in the list, but when I try to reuse them for new conversion runs (with same CSV file even), I get the error "This map is corrupted."

Note that a couple of older maps I have made earlier (whom are not useful to me now) are still in the list and I can select and apply them to the file without errors. Of course it is not the format I intend, but they work without errors.